Digitalis spp., foxglove

Summary

A very common plant, both in the garden and the wild, with the
potential to kill in quite small amounts but also the source of
medication which has saved thousands of lives since its discovery in
1775.

Common Names and Synonyms

How Poisonous, How Harmful?

Contains cardiac glycosides called digitoxin, digitalin, digitonin,
digitalosmin, gitoxin and gitalonin. During digestion these produce
aglycones and a sugar. The aglycones directly affect the heart
muscles.

It produces a slowing of the heart which, if maintained, usually
produces a massive heart attack as the heart struggles to supply
sufficient oxygen to the brain. The acceleration of the heart ahead
of this, sometimes leads to it being wrongly said to increase the
heart rate.

The raw plant material is, however, emetic and eating a large
amount may
produce vomiting thus expelling the cardiac poisons before they can
do serious harm.

Watch a Short Video

This three minute video has a soundtrack extracted from a
'Lethal Lovelies' talk given in November, 2008.

Incidents

In April 2010, Lisa Leigh Allen of Denver Colorado entered a plea
of guilty to felony assault as part of a plea bargain agreement. She
had been accused of attempted murder after a meal of spaghetti and
salad, fed to her husband, was found to have foxglove leaves in the
salad. She was sentenced to four and a half years in jail.

Her husband, who required hospital treatment for severe
gastrointestinal upset and heart problems, apparently thought
the salad tasted unusually bitter but assumed it was just one of
those fashionable herb leaves which seem to appear from time to
time.

A young plant showing the similarity of the
leaves to other plants

In 2005, an amateur botanist committed suicide by eating foxglove
leaves. Knowing of their emetic effect, he limited his
consumption to two leaves. It was twenty-four hours later
before he suffered a fatal heart attack.

A retired hospital pharmacist told of a young man admitted to
hospital after making himself a ‘herb’ quiche using foxglove
leaves. His heartbeat became extremely slow and, for a couple of
days, it was impossible to measure the digitalis level in his
bloodstream as it was far above the maximum which the instruments
could record. It took several days of intensive care for the level
to subside and his heart rate to return to normal.

There are a number of instances of poisoning as a result of
drinking herbal tea mistakenly made with foxglove leaves.
Generally, the confusion appears to arise with
Symphytum leaves.

In 2006, Charles Cullen was sentenced to multiple terms of life
imprisonment in the USA after confessing to 29 murders of patients
at hospitals where he worked as a nurse. His preferred weapons were
lethal injections of digoxin or insulin. He may have killed another
11 but, it seems, their illnesses may have killed them before the
injections could have an effect.

Folklore and Facts

John Gerard said of foxgloves ‘They are of no use, neither have
they any place amongst medicines, according to the Ancients.’ It
was the 18th century before the therapeutic properties of the
foxglove were documented.

In 1775, Dr. William Withering was asked to comment on a family
recipe for the treatment of dropsy which had come from an old woman
in a village in Shropshire. Dropsy, a condition where the soft
tissue swells due to an increase in fluid retention was, at the
time, treated symptomatically. That is, diuretics were used to
remove the fluid. It is now known that congestive heart
failure results in a build up of fluid in the lungs as well as the
soft tissue. Withering’s early experiments with foxglove were
performed on poor patients who attended a weekly two hour free
clinic which he offered and, in seeking to use the plant as a
diuretic he, by his own admission, achieved little success.

He was inclined to give up his work with the foxglove when he heard
from his friend, a Dr. Ash, that the principal of Brazen Nose (now
called Brasenose)
College, Oxford had been cured of Hydrops Pectoris, a sort of dropsy
of the lungs, by means of the root of the foxglove. When Withering
was able to obtain a supply of dried leaves, giving him the chance
to measure dosage more accurately, he embarked on a series of trials
all of which he set down in detail, even those which failed.

By 1785, when his ‘An Account of the Foxglove’ was published,
Withering had demonstrated the benefit of using foxglove to treat
dropsy even though he assumed its success to be based on its
properties as a diuretic rather than having a direct cardiac effect.

Digitalis purperea 'Alba'

Withering’s place in the history of the development of medicine
relies on three things; his willingness to look at a folk remedy to
see if it had any merit when most of his contemporaries would have
scorned such an enquiry, his lack of vanity in publishing all of his
trial results even those which indicated failures in his treatment
of patients, but his greatest legacy is much more general than just
the use of the foxglove.

At some point in his work, Withering had what may be described as
an ‘Emperor’s New Clothes’ moment. He realised that there was
nothing about the look of Digitalis which would lead you to conclude
that it could be used to treat dropsy and, against the then
conventional wisdom, concluded that the Doctrine of Signatures was
without merit. This revelation freed doctors from the bounds
of only looking for remedies from plants which met the criteria of
the Doctrine of Signatures and, I believe, began a much more
rationally based investigation of disease and its treatment.

There are a number of explanations offered for the name
'foxglove'. It is said that it was originally named 'folk's love'
meaning the fairies loved the way the flowers point downwards as it
gives them a place to shelter. As home to the fairies, children were
told it was bad luck to disturb the plant as this would lead to the
fairies being homeless.

It is also said to come from 'fox glove' as the fairies gave the
flowers to foxes to wear as gloves so as to leave no trace when
raiding a hen house. This explanation was popular with people
inclined to raid the rich man's hen house for themselves.

Numerous people have told me about playing with the flowers
of foxgloves, as children, without coming to any harm but you
will still see alleged experts saying that it should be removed
from any place where children might be present.

Digitalis lantana is the species grown commercially for
pharmaceutical use.